The motion of a vehicle is governed by the forces generated between its tires and the road (e.g., lateral tire forces). It is, therefore, advantageous for vehicle control systems, which enhance vehicle handling and increase passenger safety, to have knowledge of lateral tire force characteristics and adapt to road conditions accordingly. To meet increasing industry standards and heightened consumer expectations regarding vehicle safety, vehicle control systems should adapt to road conditions as well as vehicle conditions. To adapt to vehicle conditions, vehicle control systems can monitor parameters such as steering input, vehicle loading, and tire cornering power.
Tire cornering power, otherwise known as tire cornering stiffness or effective aligning stiffness, is a tire parameter that affects vehicle steering, handling and stability. Tire cornering power can be defined by the relationship between tire lateral forces and tire slip, and depends upon factors such as steering input and road conditions, as well as vehicle conditions such as vehicle loading, tire tread wear, tire damage, and tire inflation pressure.
Tire cornering power estimation and monitoring have not been incorporated into existing vehicle control systems due to various limitations in existing estimation methods. Known estimation methods, which typically estimate tire forces using accelerations or vehicle speed with a steady-state assumption, can be non-robust or inaccurate. Additional estimation methods, which suggest use of Global Positioning System (GPS) and Inertial Navigation System (INS) sensors to estimate a vehicle's tire cornering stiffness using a sideslip estimate to find tire slip angle, can be both impractical and costly due to a need for additional sensors on the vehicle.